<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>line_drip</title>
  <link rel="stylesheet" href="./css/line_drip.css" />
</head>

<body>
  <div class="wrap"></div>
  <div class="drip"></div>
  <script src="./js/jquery-1.11.1.min.js"></script>
  <script>
    var len = 30;
    for (var i = 0; i < len; i++) {
      var $wave = $('<div class="center"></div>');
      $wave.css({
        width: 20 * (i + 1) + "px",
        height: 10 * (i + 1) + "px",
        top: "calc(50% + " + i + "px)",
        "animation-delay": -10 + 0.2 * i + "s",
      });
      $(".wrap").append($wave);
    }
  </script>
</body>

</html>